There is actually a pacman templated bundled with Construct 3.
It is kind of a grid movement as well though.
It is how the original pacman would move though on the first arcade cabinets.
If what you are looking is to allow for Pacman to turn whenever you want it to, simply remove the "limitation" to allow the input to be read at any point instead of once the grid movement is done.
You possibly should look into using the 8direction behavior instead of the bullet and look into examples of implementation for it.